diamond.clj

(ns diamond.core)

;;
;; Diamond kata
;;

(def alphabet "ABCDEFGHIJKLMNOPQRSTUVWXYZ")
(def blanks-d (iterate #(str %1 "-") ""))

(defn blanks [n] (nth blanks-d n))

(defn base-line [width n letter]
  (let [outer-blanks (blanks (- width n))]
    (str outer-blanks letter outer-blanks)))

(defn diamond-line [width n letter]
  (let [inner-blanks (blanks (dec (* 2 n)))
        outer-blanks (blanks (- width n))]
    (str outer-blanks letter inner-blanks letter outer-blanks)))

(defn diamond [c]
  (when-not (or (nil? c) (.equals c ""))
    (let [width (.indexOf alphabet c)
          half-diamond (for [n (range 0 (inc width) 1)]
                         ((if (= 0 n) base-line diamond-line) width n (nth alphabet n)))
          diamond (concat half-diamond (rest (reverse half-diamond)))]
      (clojure.string/join "\n" diamond))))

(println (diamond "Z"))
(diamond "")
(diamond "A")